For the purposes of the instant application, an electrical contact refers to an electro-mechanical device that may be employed when it is desired to readily connect (or disconnect) a first-insulated conductor to (or from) a second insulated conductor. Such a device is included, for example, in a conventional telephone circuit wire connector or in a conventional telephone electrical termination block of the type that provides telephone service to a customer.
A wide variety of substrates require protection from adverse environmental conditions, including moisture, insects, dirt, plant life and corrosion deposits. In some cases, especially when electrical contacts are to be protected, it is desirable to provide a removable protective cover over the substrate, so that it is possible easily to reenter and work on the sealed substrate. It is known to use greases to protect electrical contacts, the grease being contained in a container which is applied to the electrical contact(s)--see for example U.S. Pat. No. 3,897,129 (Farrar). However, the grease is a thixotropic fluid, which places limitations on the ways in which it can be used. Furthermore, when reentry to the sealed contact is required, when the container is removed, grease remains coated on the contact(s) and must be cleaned off before electrical work can begin. It is also known to encapsulate electrical contacts within a container by means of a two-part liquid composition prepared by mixing ingredients which will react slowly together. Before the ingredients have gelled, the mixture is poured into the container, where it cures in situ to form a hard gel--see U.S. Pat. Nos. 4,375,521 (Arnold) and 4,102,716 (Graves). However, this procedure involves preparation of the liquid composition at the site, delay while the composition gels, and the need to provide a container around the contact(s), into which the composition can be poured. Furthermore, when reentry to the encapsulated contacts is required, the gelled composition cannot easily be removed.
In order to explain how an electrical contact is included in a telephone electrical termination block, attention is directed to FIG. 1 which shows a typical termination block 10. The termination block 10 includes a plurality of binding posts 12 which are, in fact, the electrical contacts. The binding posts 12 each comprise a small screw-type contact that facilitates the connection or disconnection of the first and second insulated conductors. Here, the first conductor may comprise a drop or service wire 14 that is wrapped around the screw-type contact so as to provide a connection between the customer and the termination block 10. The second conductor, on the other hand, may comprise a cable stub 16, which is pre-wired to a hermetically sealed portion of the termination block 10.
Although an end lead of the cable stub 16 is hermetically sealed within a portion of the termination block 10, the binding posts 12 (which connect one end of the service wire 14) may be exposed to the outside environment. The binding posts 12 are typically kept in this exposed condition in order to facilitate a craftsperson's reentry to the termination block 10 in order to effect repairs or change a service connection.
If the binding posts 12 remain exposed but unprotected from the outside environment, they may be affected by environmental agents including dirt, plant life, moisture, corrosion deposits and insects. These agents, however, can be adversative to the termination block 10 because they may effect a conductive bridge between some or all of the binding post contacts. This conductive bridge, in turn, may provide a means for the creation of noise and may produce an electrical short-circuit within the termination block. It is noted in particular, that such termination blocks that are left unprotected within humid or moist environments can incur a critical loss of insulation resistance between binding post contacts which can result in a temporary or permanent disruption of termination block operation or customer service.
In order to avoid disruption of service, therefore, it is important that the termination block be maintained so that it is resistant to the cited adverse environmental agents and can remain moisture insensitive. Consequently, it is important that the binding posts contacts (or electrical contacts) be provided with a protection means (of the type indicated generally by numeral 18 in FIG. 1) that insures their reliable and safe operation within an otherwise adverse and moisture-laden environment.
In order to select an appropriate protection means for electrical contacts, it is advantageous to realize the following design objectives. Thus, the protection means should not obstruct or delay a craftsperson's access to the reentrable electrical contacts. At the same time, and as its name suggests, the protection means should protect the electrical contacts from the above described adverse environmental agents, including a high humidity environment. To these design objective ends, it is advantageous that the protection means utilize materials that are non-hazardous, possess acceptable electrical properties including a desired insulation resistance and remain substantially inert toward a molded plastic substrate which typically houses the electrical contacts.
Embodiments of the present invention fulfill this need and satisfy the design objectives by providing a unique apparatus and method for protection of electrical contacts. The apparatus of the present invention does not obstruct or delay a craftsperson's repeated reentrys to the electrical contact. At the same time, the present invention safely protects the electrical contacts even when they are exposed to an adverse environment. The present invention may consequently be employed with a variety of electro-mechanical devices like connectors or termination blocks where it is important to have ready access to the device while insuring, nevertheless, that the device is protected from the adverse environment.
It is also well known to splice (i.e. connect) electrical wires by placing them within a connector and then permanently deforming the connector by mechanical pressure--see for example U.S. Pat. No. 4,208,788 to Siden. If the electrical wires so spliced are to be used in a corrosive, moist or hazardous environment, it is desirable to provide an environmental seal in association with the pressure connector in order to maintain an acceptable electrical connection between the electrical wires.
Such environmental seals are known and include, for example, a special box which is designed to house the wire splice. In practice, however, the special box does not provide a hermetic seal; ultimately, moisture and/or other foreign substances may permeate the special box and induce corrosion within the wire splice.
Other known environmental seals include a method of covering the spliced wires with a silicone grease. The silicone grease, however, is unsatisfactory since it can coat apparatus that should remain clean, and is displaced by vibration.
Environmental seals further include a crimp splicer wherein there is an associated insulating heat shrinkable sleeve which is adapted to retain a crimp barrel therein. In practice, the heat shrinkable sleeve may be shrunk down around the barrel and electrical wires in order to protect the splice from the environment. In some cases, however, it is disadvantageous or even prohibited, to employ a heating unit to heatshrink the sleeve.